Bad spot to overcall?

[Beck]

Pokerroom 20+2
Blind 200/400

SB (Hero) 2000 is dealt ATs
BB 5500
UTG 1600
BUT 5900

UTG goes all in, BB calls, Hero??

Button had been quite passive, so my proces of thoughts was, that he would perhaps just check it down, not forcing me out. If he did bet, he probably had a hand, I could then fold, and UTG would hopefully be out.
If I did hit the flop on the other hand, I had a good chance of trippling up, and a shot for first place.

[DownLow]

How can the BB call before the action is to the SB (is the caller actually the button)?

To answer your question, I certainly fold this hand. While UTG is desperate and could be pushing with any 2, I think the Button has a range of hands that AT is not doing well against. I would think the button might call this with AK-AT, any pocket pair. You are only a coinflip to a low PP and a big dog to a high PP. If you fold this hand, you still have T$1800 which has at least a little fold equity against the blinds. If you call and UTG wins, you are almost certainly out in 4th. If you call and Button wins, you are out in 3rd with no chance to move up. If you fold and UTG loses, you have enough chips to make some moves to get better than 3rd place. You also have to consider there is another big stack behind you that has yet to act. I think AT in this situation is a clear fold. Hopefully somebody with better math skills than I will give a +-EV calculation for this hand.

[Beck]

Oh, I mistyped the first post. Button was the one to call UTG's all in.

In hindsight I totally agree with you! But wanted to check with you guys, as I've previously given a lot of thoughts to the situations, and still been wrong...